Circuit control device for transformers



July 22, 1941. M. F. MrrscHRxcH 2,250,165

CIRCUIT CONTROL DEVICE FOR TRANSFORMERS Filed Dec. 21, 193s 2 sheets-sheet 1 T f )MMM July 22, 1941. M. F. MlTscHRlcH 2,250,165

CIRCUIT CONTROL DEVICE FOR TRANSFORMERS Filed Dec. 21, 1938 2 Sheets-Sheet 2 MUM/MM BY Arron/vw MMM Patented July 22, 19 41 CIRCUIT CONTROL DEVICE FOR TRANSFORMERS Melville F. Mitschrich, St. Louis, Mo., assigner to Moloney Electric Company. St. Louis, Mo., a

corporation of Delaware Application December 21, 1938, Serial No. 246,933

(Cl. 20o-122) 8 Claims.

This invention relates to circuit control devices for transformers, my present application being a continuation, in part, of my application Serial No. 105,166, filed October 12, 1936.

.One object of my invention is to provide a transformer-circuit control mechanism of novel construction; that affords a high degree of protection to workmen or other persons who service the transformer, inasmuch as it is designed so that the transformer is cut into and out 'of service by bodily movement of an element or part operable from the exterior of the transformer tank and designed so as 'to bridge the space between two contacts, one of which consists of a coil contact that is located on the interior of the transformer tank.

Another object is to vprovide a transformer circuit control mechanism, in which the bodily removable device or element used to open and close the transformer circuit is of such design and construction that it can be installed and removed easily by a conventional linemans insulated hook stick in the hands of an operator located at a point remote from the place where the coil lead extends out of the transformer tank.

Another object is to provide a circuit control mechanism for an oil-cooled transformer that is operable from the exterior of the transformer tank, and which is of such construction that when it functions to open the transformer circuit, the oil in the transformer tank will assist in quenching the resulting arc.

Another object is to provide a transformer circuit control mechanism of the kind above described, which is equipped with a novel means for automatically opening the transformer circuit, and disconnecting the transformer from the line.

And still another object of my invention is to provide a circuit control device for transformers,

which, in addition to insuring safety to persons who service transformers, is of such design or construction that it can be easily changed or varied to adapt it to transformers having different current and heating characteristics. Other objects and desirable features of my invention will be hereinafter pointed out.

To this end I have devised a transformer circuit con-trol mechanism that comprises a bodily removable device or element that completes the circuit between a line contact on the exterior of the *transformer tank, and a coil contact on the interior of the tank that is connected to a coil lead of the transformer. Said bodily removable device or element can be constructed in various ways without departing from the spirit of my invention, but it is preferably of such construction that it; can be easily installed in or removed from an insulator on the transformer tank by a conventional linemans insulated hook stick, thereby enabling the transformer to be cut into and out of service, without the necessity of the lineman coming in close proximity to the coil lead thatextends out of the tank. In the preferred formi of my invention herein illustrated the circuit control mechanism is designed so that it will act automatically to disconnect the transformer from the supply line, in the event the current is of such magnitude and proportion as to probably result in injury or damage to the transformer insulation, or in the event there is some other defect in the transformer which will cause excessive current to flow.

Figure 1 of the drawings is a fragmentary vertical sectional view of a transformer circuit control mechanism constructed in accordance with my invention, illustrating said mechanism in operative position for establishing electrical connection between the line contact and the coil terminal or contact on the interior of the tank.

Figure 2 is a similar view, taken at approximately to Figure 1.

Figure 3 is a fragmentary view, partly in side elevation, illustrating how the bodily removable element or device of the circuit control mechanism may be released and removed from fthe transformer tank preparatory to servicing the .transformer or performing some operation on same.

Figure 4 is a top plan view of the part shown in Figure 3; and

Figure 5 is a side elevational view of the parts illustrated in Figure 3, but showing the bodily removable element of the circuit control mechanism locked or latched in operative position.

In the accompanying drawings which illustrate my invention, l designates the cover of the tank of an oil cooled transformer, T designates as an entirety the core and coil structure of the transformer, and :c designates the oil in which said core and coil structure is submerged. Some portion of the transformer tank, such, for example, as the cover i, is provided with an insulating bushing 2, in which is mounted a bodily removable device or element that is usedv to establish electrical connection between a line contact or terminal 25, herein illustrated as being located on the exterior of the transformer tank, and a co-acting contact or terminal 3 on the interior of *the transformer tank that is connected to one of the con leads u. the said con contact 8 being submerged in the oil x, as shown clearly Ain Figures 1 and 2. The external line contact or -used to establish electrical connectionv between the external contact 2l and the internal .contact I comprises a body part formed preferably by a tubular member 4 of insulating material, which is made of such diameter with relation to the diameter of the opening in the insulating bushing 2 that it can be easily inserted in and withdrawn from said bushing by means of a conventional linemans insulated hook stick or other suitable hot line tool that is engaged with a part at the upper end of said tubular member 4. At the lower end oi the body part 4 of the device is a metal tip 5 that is adapted to co-act with the coil contact 3, and at the upper end of said body part is a metal cap Ii that is adapted to co-act with the external contact or terminal 25. When the body part 4 is in operative position, the cap i8 snugly engages the external contact 25, and the metal tip 5 snugly engages the internal coil contact 3.

In the preferred form of my invention herein illustrated there is an electrical conductor 26 on the interior oi' the body part 4 that leads downwardly from the metal cap I8 to a contact or switch point I4 secured to the interior of the body part 4, and arranged in spaced relationship with a similar contact or switch point I3 that is mounted on the interior of the body part 4 adiacent the lower end of same. The contact or switch point I l is electrically connected in any suitable way with the metal tip 5 at the lower end of the body portion 4 of the device. Normally,

the spaced contacts I3 and I4 are maintained in electrical connection with each other by means of a contact blade I Il, with the result that the circuit will be completed between the internal coil contact I and the external line contact 25. I'he contact blade I0 is arranged on the interior of the body part 4 of the device, and is attached at its upper end to a contractile spring I2 positioned on the interior of the body part 4. At the lower end of the contact blade I0 is a hook I I (see Figure 2) that cooperates with the thermal element I to normally hold said contact blade in v such a position that said blade is in engagement with the contacts I3 and I4. In the event of excessive current ilow that might damage the transformer, the thermal element 'I flexes or moves in a direction to release the contact blade I0, whereupon sad blade will move upwardly, under the influence of the spring l2, into such a position that said contact blade will be disengaged from the contact i3, thereby causing the transformer circuit to be automatically opened. In order that the contact blade I0 and the contact Il will be sure to be submerged in oil when said contact blade moves in a direction to open the transformer circuit, the body part 4 of the device is cut awayor provided with slots or other suitable openings, as shown in Figure 1, so as to permit the oil in the transformer tank to circulate freely through the interior of the body part 4 of the'device, and thus assist in quenching the arc that results upon movement of the switch blade I..

' The thermal element 1, previously mentioned. co-acts with a heating coil l that is positioned inside of the metal tip l at the lower end of the body part 4 of the device, said heating coil being so constructed and arranged that when the device is mounted in operative position in the transformer, the electric current will pass through said coil and the heat generated by the coil. in the event of an excessive current ilow, will be applied to the thermal element 1. As shown in Figure 2,4

the thermal element 1 (which may be bimetallic or some other type), is attached to a metallic part on the interior of the body part 4 of the device which carries the contact Il. Said thermal element 'l is of loop form in general outline, and is provided with a flexible arm or portion that projects upwardly into the zone in which the lower end portion of the contact blade I 0 lies when the transformer circuit is closed. At the extreme upper end of the upwardly-projecting portion of the thermal element 'I is a retaining device 'I' that laps over the hook II on the contact blade Il. Under normal conditions the thermal element I will co-act with the hook II to hold the contact blade lli retracted. However, in the event of a dangerous overcurrent, the heat generated by the coil 6 will cause the free end of the thermal element 1 to flex to the right, looking at Figure 2, into a position where the retaining device 1 thereon is disengaged from the hook II on the contact blade, whereupon said contact blade will move upwardly under the influence of the spring I2 to automatically open the transformer circuit. In order that the device may be easily used with or adapted to transformers having different current and heating characteristics, the metal tip l which carries the heating coil l is so constructed that it can be easily detached from the body part 4 of the device and replaced by a tip equipped with a coil having different characteristics. In the device herein illustrated the metal tip 5 is combined with the coil l, so as to form a unit that is detachably connected to the lower end of the body part of the device by screw threads, but it will be obvious that the particular construction of the metal tip 5 and heating coil I, and the way said parts are combined with the body part 4 of the device, is immaterial, so far as my broad idea is concerned. In the form of my invention herein shown, the contact blade I0 is of substantially T-shape in horizontal cross section, or, in other words, consists of a substantially bar-like member provided at one edge with laterally-projecting integral flanges, the upper end portion of said bar-like member extending upwardly beyond said flanges, so as to form a part to which the spring I2 can be easily attached. At the lower end oi the contact blade Il a portion oi' said barlike member is cut away, so as to form the hook Il, previously mentioned. Obviously, the particular shape or form of the contact blade Il Is immaterial, so long as said blade is constructed in such a manner that it will establish electrical connection between the contacts I3 and I4 when the hook Il at the lower end of said blade is in operative engagement with the retaining device 1, and will interrupt electrical connection between said contacts when the retaining device 1 releases the hook Il, so as to permit the blade Il to move upwardly under the inuence of the spring I2 attached w the upper end of same.

The bodily removable device or element which constitutes the circuit control mechanism of the transformer is retained in operative position in the transformer tank by a locking means or latching means at ther upper end of the device, which comprises a yoke-shaped lever II pivotally mounted on the cap I6 at'the upper end of the body part I, hooks 20 on the line terminal contact 25 on the insulator 2 that lap over a portion of the lever I'I, and a pivotally mounted dog I9 on said lever that is adapted to engage a lug or projection I9* on the line terminal contact 25, said lever II being provided with a ring or eye I8 of such size and dimensions that a conventional linemans insulated hook stick can be easily inserted in the ring or eye I8 and manipulated in a way to engage and disengage the co-acting parts of the latching or locking means. To remove the device from the tank it is only necessary to engage the hook stick with the eye I8 and exert an upward thrust on said stick, so as to trip the latch or dog I9 and permit the lever II to be rocked upwardly in a direction to release it from the retaining hooks 20 on the line terminal contact 25, whereupon the body portion 4 of the device can be moved upwardly through the insulator 2, as indicated in Figure 3. To install the device in the transformer tank the hook stick is engaged with the ring or eye I8 of the device, and is then moved in a direction to position the device above the insulator 2 in alignment with the opening in same, after which the device can be slipped downwardly through the insulator, so as to cause the metal tip 5 at the lower end of the device to engage the coil contact 3 and cause the metal cap I5 at the upper end of the device to engage the line terminal contact 25 on the insulator, the stick being manipulated so as to insert a portion of the lever Il under the hooks 20 on the insulator, and thereafter cause the latch I9 to snap into engagement with the locking element I9a with which it co-acts. It will, of course, be understood that preparatory to introducing the device into the transformer tank, the contact blade I is moved downwardly. so as to cause the hook II on the lower end thereof to snap into engagement with the retaining device IEL on the thermal element 'I, such movement of the contact blade I0 being effected by exerting downward pressure on a finger piece Il)a carried by said contact blade.

If desired, the bodily removable element of the circuit control mechanism of the transformer may be provided with a visual signal for showing the condition of the transformer circuit (whether open or closed), when said element is arranged in operative position in the transformer tank. In the form of my invention herein illustrated the upper end of the contact blade I0 is connected by means of a flexible element, such as a wire or metal ribbon 29 with a disk connected to a rock shaft that carries an indicator I5, the rock shaft to which said indicator I is connected being mounted in the metal cap I6 of the device and designated by the reference character I5` and the disk on said shaft to which the wire or ribbon 29 is attached being designated by the reference character |50. A coiled spring I 5b is combined with the rock shaft I5EL in such a way as to normally exert pressure thereon in a direction tending to turn said shaft into a position to hold the indicator I5 in its upright or active position. When the contact blade I0 moves upwardly under the influence of the spring I2 to open the transformer circuit, such movement of the contact blade I0 relieves the load imposed on the rock shaft I5*l by the flexible element 29, and consequently, the indicator I5 moves automatically into its active position, under the influence of the spring l5b that is combined with the rock shaft I5, remaining in the said active position, and thus giving notice, even to a person located at a remote point, that the transformer .circuit has been interrupted.

The main advantage of a transformer of the construction above described is that it affords a high degree of protection to linemen or other persons who may inspect or work on the transformer, due to the fact that the circuit control mechanism comprises a bodily removable device or element which bridges or establishes electrical connection between two spaced contacts, one of which consists of a coil contact located on the interior of said tank, said mechanism being of such construction that when the circuit is opened, any arc that may form cannot cause injury to the workman or to a fragile part of the transformer. After said device or element has been removed, the workman knows absolutely that the transformer is cut off from the line, and that it is safe to work on the transformer. In this respect the'transformer is a decided improvement on transformers of the type in which the circuit is controlled by a device that always remains on the transformer, and which, through failure of one or more parts of same, might be in a condition to permit current to pass from ythe line to the coil structure of the transformer, even after the device has been actuated to cut off the transformer from the line. The bodily removable element of the circuit control mechanism may be arranged either in the primary or secondary of the transformer, and as it is constructed in the form of a self-contained unit, it can be inspected or repaired quickly, and with perfect safety. While I have stated that it is equipped with a thermally controlled means for governing the retaining device that holds the switch blade closed or in its normal position, I wish it to be understood that my broad idea contemplates the use of any suitable type or kind of device operated by current in the transformer circuit for automatically effecting the release of said retaining device under certain conditions. The fact that the bodily removable element of the circuit control mechanism can be installed and removed by a hot line tool also increases the safety factor of the transformer and facilitates the servicing of same, because it overcomes the necessity of the lineman being in relatively close proximity to the line leads and coil leads when the transformer is being cut into and out of service. I prefer to mount said bodily removable element in the insulator to which the line lead is attached, but this is not absolutely essential, as said element might be mounted in a tank insulator separate and distinct from the one employed to insulate the coil lead from the tank. In addition to making a transformer safe, my invention effects a considerable saving in the cost of servicing transformers; it produces a neater installation; it provides a circuit control device that can be easily changed to adapt it to the current and heating characteristics of the particular transformer on which it is employed, and in the event of excessive current flow, it automatically disconnects the transformer from the lines and gives notice, by means of a shiftable, visible signal, that the transformer has been cut oli' the line.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A circuit control device for transformers,

consisting of a unit adapted to be removably mounted ln an insulator on a ytransformer tank foi completing the circuit from a line contact to a coil contact on the interior of the transformer tank, said unit comprising a body portion constructed so that it can be installed in and removed from the insulator by a "hot line" tool, and said body portion having built into same a spring-actuated switch for controlling the transformer circuit, a retaining means for holding said switch in its closed position, and a mechanism operated by current in the transformer circuit for rendering said retaining means inactive so as to permit said switch to function to open the transformer circuit under certain conditions.

2. A circuit control device of the kind described in claim l, in which the current operated mechanism that renders the switch retaining means inactive, is constructed in the form of a variable, replaceable element.

3. A circuit control device for transformers, consisting of a unit adapted to be removably mounted in an insulator on a transformer tank for completing the circuit from a line contact to a coil contact on the interior of the transiormer tank, said unit comprising a body portion constructed so that it can be installed in and removed from the insulator by a hot line tool, said body portion having built into same a switch blade that co-acts with contacts in the transformer circuit, a spring for moving said blade in a direction to open the transformer circuit, a retaining means for normally holding said blade in a position to maintain the transformer circuit in a closed condition, and a means rendered operative by an abnormal condition in the transformer circuit for causing said retaining means to release said switch blade.

4. A circuit-control device for transformers, consisting of a unit adapted to be removably mounted inan insulator on a transformer tank, for completing the circuit from a line contact on the exterior of the transformer tank to a coil contact on the interior of the transformer tank, said unit comprising a body portion constructed so that it can be installed in and removed from said insulator by a straight line push or pull imparted to said body portion by a hot line tool, and a retaining means for holding said unit in the insulator, carried by said body portion and constructed so as to be capable of being manipulated by said hot line tool during the operation of installing or removing the unit.

5. A circuit control device for transformers, consisting of a unit adapted to be removably mounted in an insulator on a transformer tank, said unit comprising a body portion of substantially tubular form or shape, an automatically operating switch housed within said body portion for completing the circuit from an external line contact to a coil contact on the interior of the transformer tank, and a control mechanism for said switch governed by current in the transformer circuit and comprising a variable,

replaceable element adapted to be operated by current in the transformer circuit. i

6. A circuit control device of the kind described in claim l, equipped with a visible signal that -shifts automatically into a different position and remains in said position, whenever said switch functions to open the transformer circuit.

7. A circuit control device for transformers, consisting of a unit adapted to be removably mounted in an insulator on a transformer tank, said unit comprising a body portion of substantially tubular form or shape that has a sliding fit with said insulator and which is adapted to be installed in or removed from said insulator by a straight line push or pull with a hot line tool, a reciprocating switch blade in said body portion, a retaining device in said body portion for holding said switch blade in a position to complete the circuit from an external line contact to a coil contact on the interior of the transformer tank, a spring for moving said switch blade in a direction to interrupt the circuit between said contacts when said retaining device is rendered inactive, and a coil built into said unit and adapted to be energized by a current in the transformer circuit when said unit is installed in operative position in the insulator for rendering said retaining device inactive under certain conditions.

8. A circuit control device of the kind described in claim 7, in which said coil is carried by a removable metal member, at the lower end ef said body portion that engages the ccil con`- tact on the interior of the transformer tank.

MELvnLE Ffm'rscHRicH. 

